This invention relates to a closure for sealing a food container. More particularly, it relates in one aspect to a composite closure having visual sealing force indicating means, and in another aspect to a closure having a ratchet operated tamper indicating band.
Composite closures are widely used to seal food containers, for example wide mouth containers which are "retorted" after sealing. Such closures comprise a sealing disk or cover, usually of metal or alternatively plastic, which is encircled and housed within a separately formed molded plastic ring or shell. The disk has a raised peripheral bead which presents a downwardly opening groove that contains a sealant or gasket for forming a seal with a sealing rim around the top or finish of the container. The ring holds the disk down on the container but is rotatable relative to the disk so as not to turn the disk on the container, which would greatly increase the torque required for opening or closing. This type of seal is relatively insensitive to the thermal expansion and contraction that occur during retorting. (In retorting, after the container has been filled it is heated to a temperature above about 220.degree. F. under external pressure to sterilize the food sealed in it.)